The Effects of TSH level on the Results of F-18 FDG PET/CT in Recurrent Differentiated Thyroid Carcinoma Patients with Elevated Serum Thyroglobulin Level and Negative I-131 WBS.

Document Type : Original Paper, Oncology

Author

National Cancer Institute , Cairo University

Abstract

Purpose : To assess the effects of TSH level on F-18 FDG PET-CT results & its impact on serum thyroglobulin (TG) cut off point and management in recurrent DTC patients with elevated TG level & negative I-131 WBS. Material
and Methods: This prospective work involved 38 histopathologically proved DTC patients underwent total thyroid ablation with elevated serum TG and negative I-131 WBS during follow up. F-18 FDG was done in all patients using standard technique. Results: Patients divided into two groups: (I) Stimulated TSH group (i.e. TSH level > 30 IU/L, 60 ± 20 IU/L): 20 patients. (II) Suppressed TSH group (i.e. TSH level <0.1 IU/L, 0.007 ± 0.003IU/L): 18 patients. Significantly higher overall accuracy, sensitivity & NPV were found in stimulated group (98.5%, 88.6%, 62% respectively) compared to the suppressed group (66%, 62% & 31.5% respectively) that was more obvious in nodal rather than pulmonary deposits (P<0.05). However no significant difference was demonstrated in specificity & PPV between both groups. Significantly lower TG cut off point was demonstrated in stimulated group (15 ng/ml) compared to suppressed group (21 ng/ml) (P<0.05). Moreover significantly higher impact of F-18 FDG PET-CT in TSH stimulated (40%) was demonstrated compared to TSH suppressed (11.2%) group on patient management.
Conclusion: High TSH seems to enhance F-18 FDG PET/CT efficiency on nodal rather than pulmonary metastases in recurrent DTC patients with elevated serum TG level and negative I-131 WBS. Moreover it reduces TG cut off point for F-18 FDG PET-CT & escalates its impact on patient management.

Keywords

Egyptian Journal Nuclear Medicine
Volume 6, Issue 6
December 2012
Pages 40-54

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